Composition, process, and product



May 12, 1959 V K. lLER ETAL- comosnrou, PROCESS, AND PRODUCT Filed July3;, 1956 INVENTOR S RALPH. K. ILER ARTHUR G.v JEL INEK ATTORNEY United,st t si m v 2,886,466 v s 3 COMPOSITION, PRo'cEss, AND PRODUCT Ralph K.Iler and Arthur G; Jelinek, Brandywinellunr dred, Del., assignors toEJI. du Pont de Nemours' and Company, Wilmington, Del., acorporation ofDela ware I Application July31, 1956, Serial No. 601,122 1"2 Claims. Cl.117-65) v This invention relates to compositions and processes forbinding inorganic fibers and to'the products'produced,

and is more particularly, directed'tosuch compositions a clay, and'analuminum salt, to mixing inorganic fibers with said comprising a silicasol, processes comprising composition, drying-the mixture,and heatingthe dried mixture to an elevated temperature, and to the products,

comprising a mass of inorganic fibers firmly boundto gether With thesilica alumina-clay-containing binde'r re m the. heating of thesol-clay-salt mixture at sulting fro elevated temperature.

'In the drawing a product of the invention is illustrated" peratures.Since the value of inorganic fiber insulation isf'gr'eat est at hightemperaturesthis deficiency of organic ss r'i 'i e a un r Inorganicmaterials, such as silica solsfclay suspensions lnorganic fibers 1 areheld to- F juncture with a deposited'mass 30 have been used'bntaresubject to"'decompositio'fiat elevated te'm-.

silica sols.

present invention ordinarily is an aquasol, but organosols evenpreferred as, I for example, when the fibers to be bonded are hydro- H2,886,466 Patented May 12, 1959 The colloidal silica sol'used incompositions of the are also effective and sometimes are phobic andhence difiicult to wet.

The art is already familiar with methods of making Repeptizin'g a-silicagel, as described in United States Patents 1,835,420 to method.Organosols can be' made by-such methods as ,wmixing solutions ofsodiumsilicate and acid and precipitating the metathetically formed saltby adding a large contain from 12 to 3,5% SiO j The silica sol shouldcontain silica .trolled .growth of the particles as described in, United"States Patents 2,574,902 to Bechtold and 485 to Rule, and 2,705,345 toAlexander. These sols.

proportion of an organic liquid. Methods adapted to give relativelysmall silica particlesinclude' removing sodium ions from sodium silicatewith ion-exchange resins as. ,,.taught in Bird United States Patent2,244,325 "hees United States Patent 2,457,971; r a

, Especially preferred for use in the binders of the. present invention,however, are the sols of dense, substantially discrete, amorphous.silica particles prepared by concontain a type. of particle whichappears to :give superior strength tothebinder compositions. "Iheyordinarily particles, in the range of, 3.:to l50 millimicrons (mg) inaverage diameter,,;

ltiislpre'ferredtofuse sols of 10 to 50 m particles, and

sols of discrete, substantially spherical amorphous silica particles 12to 20 m .in diameter are. of greatestQsuitability.

such methodsas merely n and the like, have been used'as binders, eitheralone or" I in combination. Such: systems are thermally stable butunfortunately; the bonded articles lack mechanical strengthso'that theinorganic binders heretofore available ha ,left niuch'to'be desired. ,1j H I {Nowfaccordingto'the present invention it has-b'e'en'.foundifthat'by incorporating a component 'yieldin'galumn nfum ons insolution into 'cc'alloidal silica jsol-clay compositions' in suitableproportions novel and especially -advanta-geous bonding; materials areproduced, and that by employing such"a"birider with 'm rga i'c'nbers anddrying. thefmixture", formed articles "are 'produced' having V provedstrength, especially after exposure 'tohi'g'h'tem' peratures. The bindercompositions; advantageously contain modifying agents for specialpurposes.

The efiect of adding the component yielding aluminum ions, such as analuminum salt, is quite unexpected, since it-has been knownthatpolyvalent ions 'g'enerally,-and*especiallyaluminum ions, ,w'ill.precipitatekilica sols as' gelsw-having-littleor no value as binders.Evidently in the compositions? of the present invention there isa'synergism between' -the aluminum ion, the' silica sol,-and the" claywhen these components are present in the critical proportions, and thissynergisticcooperation gives rise I kaolins, are especially preferred.These are widelyavail-I used any' of the complex silicatescommonly'referredjto by this term. Mont'morillonites, includingbentonite,

While a large number of silica sols which give excellent results a'rethus available, it will be understood that the V low molecular-weight,unstable sols containing particles. smaller than 3 millimicrons indiameter and preparedbyv 'eutr'alizing sodiumsilicate withacid withoutsubsequentstabilization are not practicable and tobeavoided.v f

i As the clay inabinder of this invention there c an-be which swellinwater, can beemployed, but their tendency to holdlargeproportions ofbound water and to .be. dimensionally unstable make them less desirable.Clays of special properties, such as attapulgite and Ihalloysite,

can be used, often to advantage, but their limited occurrence in natureand consequent higher cost restrictstheir adoptionon a large scale. i

, Non-swelling clays of the kaolinite type, specifically able at verylow cost, and since theyhavesubstantial dimensional' stability in water,problems such as unduethickening of the binder and dif iiculties'occurring durm'wgdrying are obviated.

The clay particles should be less than 1 0 microns in' d ameter and atleast 50% by weight shouldbe less than.

ticlesize canreadily be ascertained by examination under an ordinarylight microscope or by conventional'sedimentation tests.

The componentof the binder supplying the ionscan be any water-solublealuminum compound, or-

solution in a manner such that Al+++ ions are'formed the aluminum is nottied complex. Soluble salts chloride; aluminum nitrate, and aluminumsulfamate can be" used. However, water-soluble salts and basic salts of,

. organic acids; especially monobasic carboxylicacids such to the highlyadvantageous and 'usefulbinderproperties.

asformic and acetic acids, are preferred. Thus'among Neundlinger or2,375,738 to White or 2,724,701 to Legal, is a common Snyder, 2,577,: I

The suitability of a clay as to par- I the preferred aluminum salts areincluded aluminum formate and basic forma't'e, 'luminum acetate andbasic acetate, and aluminum formoacetate.

The.proportions, of, silica, clay, and aluminum ion are critical forobtaining'thei'fabovefmentioned synergistic action in the binder composthe jeolloi dal silica infith Tiie total solids in the liquid bindershould be in the rangejfrom l to 60% by Weight and preferably from to'30%.* i s The pH of the binder should be from 2 to about 7.5.

'lti' will be understood cluded in the'binder compositions with uniqueand unob'vious effects. Formaldehyde condensation resins and stai'chesare in this class of modifiers. So, also, is a glycol-urea boratecomposition sold as Tybon 1016B by Booty Resiners, Newark, Ohio, inaqueous paste form havingfa 31% solidscoiitent'. The proportionof suchmodi fiei's' v'vill in genera be"a*rnino'r part of the binder-i-that is,not more than about 5%. by weight.

"Other, 7 i w A included, such "as fillers, bodying agents, againinminorproportioni s lifmaking the binder the components above-described aremixed together to give .a uniform suspension. components can be adddinany order; it is preferred, ho v' er, todisperse the clay in the silicasol containing anydesi r edniodifiers, to take advantage of the gooddispeI' ing characteristics of the clay-silica sol mixtures. If thmixture does not have a pH well down in therange of2'to 7.5 it is thenpreferable to add an acid to avoid subsequent bodying effects on thealuminum salt. The acidused can be any of the common inorganic acids,such as hydrochloric, ,or sulfuric, or the water soluble organics,

especially of thelower aliphatic type, such as formic oraiieticfiwithorwithout substituents such as chloride, bro

miiie; hydroxide groups. However, acids knownto have solubiliaingefliectonaluminum" salts should not be Einally, in a' preferred process,the aluminum salt,

ll pfre ra l asf a concentrateclsolution, is w'ith'tlieothe'ringredients.

colloidal silicaclay-aluminum ion compositions of thepre s'ent.invention exhibit outstanding advantages P as binders forin'organicfibers, particularly where such fibers are ,tg be nsed as formed bodiessuch as insulation block. ni fibers, suchasmineral fibers,- have alreadybeen bonded toshaped masses using organic resin binders, but such masseslose their strength athigh temperatures because the binder is melted ordecomposed. With binders of this invention outstanding improvement inthe strength of the bonded masses of fibers at elevated ternpelraturesiis noted. 7, "Included among the inorganic fibers which canbe so bonded are glass fibers, rock wool, asbestos fibers, and syntheticinorganic fibers, such as alumino silicate fibers.

:Tt is tobe noted that in the bonding processes of this. inve'ntionthebinderdoes. not demonstrate its strength advantage until the. fibermasses containing, the. binder k have been driedand heated to elevatedtemperature, that is, at'.from 300 C.-to,the softening temperature ofthe fibers. It is necessary tohold fthe binder-impregnated fiber massesin. shape at least until the binder has dried.1

This ican be done, for instance in the case of glass fiber that organicmodifiers can be iu- 'o're conventional binder additives can als o beagents, adhesives, resin" prodncts, wetting agents, anti-oxidants, andanti-punking added and mixed bonding the fibers with -say, 1 to,

the binder.

temperatures in excess of ganian ount in the range of lS to 10% of theirweight-of a conventional resin binder such asalkyd orphenolform'aldehyde resin, and thereafter saturating the fiber blockwith the silica sol-clay-aluminum ion binder. On the other hand it willbe evident that the fibers can be maintained in the desired physicalshape until dry, by mechanicalrnethods such as molding, or, in the caseof asbestos aspen-tor example, by applying the binder to theshcetionthepaper-forming machine.

The preferred method of, applying the binder to formed glass fiberinsulation block is byvacuum impregnation; The block is subjected to avacuumto reduce thepressure in the pores, and the block is thensubmerged in the binder. Alternatively, the binder dispersion can beflowed over the top of the block and suction can be applied underneath.It is possible to regulate the amount of binder applied by subjectingthe saturated block to controlled drainage, or by varying the solidscontent of Eollowing iinpre nation of t lhe inorganic fiber mass,

withthe binderby suchniethods as immersion or sprayy, mixing theunformed. fibers with. the binder and s thenlforming them,suitablein'eaus ofdrying is temperature ofup to 260? C.,' but lowertemperatures (70 l 0q? F.,)-,can beused and equivalent means, asdielectric drying, will be readily apparent to those skilled,in the art.

After drying, the

300 C. if desired, to burn out any organic constituents present.

Thebinder-solids content of the resultsiihdis preferred.

The i bonded articles strength, and are not fragile or many organicbinders. tAsiconipared'with articles bonded withi'silicaisolclaycompositions containing no aluminum ion, the articles have as much as100% greater compressive strength, as shown, for instance, byconventional testingmethods using the Tinius-Olsen or Testerso Thebonded articles are useful as thermal insulation, soundabsorbentmaterials, filter media, and onother' usjs'iwhere improved bondstrength of inorganic fibers is desired. e. the"following illustrativealreadygiven. In the examples, all parts and percentages are by. weightunless otherwise stated.

. T EXAMPLE 1 Abinder composition was made with colloidal silica sol,clay, and a component supplying aluminum ions. The. silica, sol.wasprepared according to a method of Rule U. "Patent; 2,577,485,contained 30% by weight of silica as SiO had an SiO :Na O weight ratioof 285:1,

and average particle diameter of the silica'was'1-7 rri illimicrons. s

f'Thgclayusedwas a Georgia kaolin identified as #2975 (Canarygtype),supplied by the Georgia Pigment Co., sandersville Ga and showed thefollowing particle sizes byasedimentationtest: t

- i 100% less than 10 microns less than 5 microns 77% less than 2microns 1T6 make the binder, 417 parts of the 30% silica solwerefcliluted with 835'parts of water and 250 parts'of the clay ,'were'.added slowly, with rapid agitation. Then a' mixture of'375 parts ofTybon 1016B anti-punking agent and 209 parts of water was added withstirring. Thegi nixturewas diluted witht3325vparts of water and. stirredvigorously, giving a dispersion having .a solids con-.; tentpf 9.3%,anda pH of 6.5 to 7.00. i

thefformed mass is dried. A yery in air-circulating ovens at a driedfiber mass should i by Weight. Ordinarily" 35% gives optimum showexcellent compressive brittleas is the case with Instron Tensile ventionwill'be-better understood by reference to examples, in addition to-thosef ing, resulted in retention, in the formation of a thin sheet.bonding was attained, and it was noted that there was The mixture wasthen acidified by adding enough 25% "formic acid (60 parts) to lower thepH to'the range of 3.2 to 3.5. The aluminum ion wasthen added in theform f'31 parts of basic aluminum formatesolution containing aluminumion equivalent. to 8.5% A1 0 One part of a wetting agent Triton X414)was then added.

This binder was used in making an article of the invention by saturatingglass fiber insulation block preformed and bonded with alkyd resin. Thevacuum saturation technique already described was used and a 400% uptakeof the 9.3% solids dispersion, followed by drainan average bindercontent of 27% in the dn'edblock.

The treated blocks were dried in an air-circulating oven at 260 C. Theresulting blocks had excellent strength.

To demonstrate the retention of strength at high temperature the blockswere heated inan air-circulating oven for 24 hours at 370 'C. Thisresulted in slow oxidative degradation of the alkyd resin binderoriginally in the blocks, as well as the Tyboniand wetting agent added;nevertheless the blocks retained nearly all of their originalcompressive strength, In contrast, blocks made and treated in identicalmanner except without the aluminum ion present retained only half theircompressive strength after the high temperature heating.

' Also, the binder was used to bondasbestos fibers (Grade 6D 20,Canadian Johns-Manville vCo., Ltd.) at 30% Excellent decidedly betterbonding in the sheet than in a comparable sheet in which the ,bindercontained no aluminum salt.

EXAMPLES 2-12 In these examples binder compositions were made in a-manner similar to that described in Example 1 but using othercomponents, in different proportions, as indicated in Table 1. Thesebinders were used for impregnating glass fiber block, with thebeneficial results observed in Example 1.

Table 1 Example S10; Ratio, 810;:

No. Particles, Clay Aluminum Salt Clay:Al O :X

17 kaolin sulfate 1:2:.0025:1 17 ball nitrate 1:10:.04:.5 150 1:4 011.56 17 attapulglte acet 6 17 rembest basicformate. 7 60 kaolinbasicchlorlde-.- l:3:.02:.5 8 17 coating acidified 1:3:.0025:.1

hydroxide. 9 30 bond ammonium 1:4:.02:.02

alum. 10 17 bleaching--. sulfate 1:2:.04:0 11 17 ceramic nitrate1:8:.01:.5 12 60 ball basic formate 1:2.5:.0025:.05

1 X stands for organic modifier, as follows: Examples 2, 4, 6-'Iybon1062-B.

Example 8-Papermakers starch.

Example Urea.

Example 7Water-soluble starch.

Example 8Polyvinyl acetate emulsion. Example 9Ortho-cres0l.

Example lO-N one.

Example 11-Water-soluble borated alkyd resin. Example 12Glyceryl borate.

We claim:

1. A binder composition comprising a sol of silica particles having anaverage diameter of 3 to 150 millimicrons, a clay having a particle sizeless than microns, and a soluble aluminum compound which in solutionforms aluminum ions, the weight proportions of the silica of the solexpressed as SiO the clay, and the aluminum compound expressed as A1 0being in the range of 1:0.5 to 10.0:0.1 to .0025, and the binder havinga pH in the range of 2 to 7.5 and a solids content of from 1 to 60% byweight.

2. A binder composition comprising a sol of silica particles having anaverage diameter of 3 to 150 millimicrons,

aluminum compound expressed as A1 0 a clay having a particle size lessthan 10 micronsa soluble aluminum compound which in solution forms.aluminum ions, and an organic modifier, the weight proportions of thesilica of the sol expressed as SiO the clay, and the aluminum compoundexpressed as A1 0 being in the range of 1:0.5 to 10.0:0.1 to .0025, andthe binder having a pH in the range of 2 to 7.5 and a solids content offrom 1 to 60% by weight.

3. A binder composition comprising a sol of silica particles having anaverage diameter of 3 to 15,0 millimicrons, a clay having a particlesize less than 10 microns, a soluble aluminum compound which in solutionforms aluminum ions, and a glycol-urea borate, the weight proportions ofthe silica of the sol expressed as SiO the clay, and the aluminumcompound expressed as A1 0 being in the range of 1:0.5 to 10.0:0.1 to.0025, and the 'binder having a pH in the range of 2.to 7.5 and a solidscontent of from 1 to 60% by weight.

4. A binder composition comprising a sol of silica particles having anaverage diameter of 3 to millimicrons, a kaolinite type clayrhaving aparticle size less than 10 microns and a soluble aluminum compound whichin solution forms aluminum ions, the weight proportions of the silica ofthe sol expressed as SiO the clay, and the aluminum compound expressedas A1 0 being in the range of 1:05 to 10.0:0.1 to .0025, and the binderhaving a pH in the range of 2 to 7.5 and a solids content of from 1 to60% by weight. w

5. A binder composition comprising a sol of silica particles having anaverage diameter of 3 to 150 millimicrons, a clay having a particle sizeless thanlO microns, and an aluminum salt of a monobasic carboxylic acidwhich in solutionforms aluminum ions, the weight proportions of thesilica of the sol expressed as SiO the clay, and the being in the rangeof 1:05 to 10.0:0.1 to .0025, and the'binder having a pH in the range of2 to 7.5 and a solids content of from 1 to 60% by weight.

6. A binder composition comprising an aquasol of dense, substantiallydiscrete, amorphous silica particles having an average diameter of from10 to 50 millimicrons, a kaolinite-type clay having a particle size lessthan 10 microns, and an aluminum salt of a monobasic carboxylic acidwhich in solution forms aluminum ions, the weight proportions of thesilica of the sol expressed as SiO the clay, and the aluminum compoundexpressed as A1 0 being in the range of 120.5 to 10020.1 to 0.0025, andthe binder having a pH in the range of 2 to 7.5 and a solids content offrom 1 to 60% by weight.

7. A binder composition comprising an aquasol of dense, substantiallydiscrete, amorphous silica particles having an average diameter of from12 to 20 millimicrons, a kaolin having an average particle size lessthan 10 microns, and an aluminum formate, the weight proportions of thesilica of the sol expressed as SiO the kaolin, and the aluminum formateexpressed as A1 0 being in the range of 1:0.5 to l0.0:0.1 to 0.0025, andthe binder having a pH in the range of 2 to 7.5 and having a solidscontent of from 5 to 30% by weight.

8. In a process for binding inorganic fibers the steps comprising mixingwith the fibers a binder comprising a sol of silica particles having anaverage diameter of 3 to 150 millimicrons, a clay having a particle sizeless than 10 microns, and a soluble aluminum compound which in solutionforms aluminum ions, the weight proportions of the silica of the solexpressed as SiO the clay, and the aluminum compound expressed as A1 0being in the range of 120.5 to 10020.1 to .0025, the proportion ofbinder to fiber being from 0.05:1 to 0.5:1 on the dry basis, and thebinder having a pH in the range of 2 to 7.5 and a solids content of l to6% by weight, drying the mixture, and heating the dried product to above300 C.

9. In a process for binding inorganic fibers the steps comprisingforming a shaped mass of the fibers, impregproduct to above 300?" C.

, hating mass with a bindercomprising an aquasol of 1 dense,substantially I I having an average diameter of from 12 to 20millirnicrons,

discrete, amorphous silica particles the aluminum ,forma'te'expressedasv A1 being. in the 1 range of 1:05 to 10.0:0.l to .0025, andthe binder having num formate, the weight proportionsiof the silica ofthe sol, expressed asSiO' the-kaofin, and the aluminum for- I v I mateexpressed asiA1- 0 'being inthe range of 1:05 to i a kaolin having anaverage particle sizev less than 10 microns,.and an aluminum vformate,the weight proportions or the. silica ot the sol expressed as .SiO thekaolin, and I a pH in the range of 2'to 7.5 and having a solids content1 :i

of from 5 to 30% by weight, the proportion of binder in the inorganifibers being from ,5 to 50% by weight on the drysolids basis, drying thebinder-impregnated fibers at j atemperature up to 260 10. A bondedinorganic shaped massof inorganic fibers bonded with the dried andheated residue of a'binder comprising a'sol of silica 'particles havingan average diameter of 3 to 150 millimicrons',

a clay having a soluble aluminum compound which in solution form-saluminum ions, the weight proportions of the'silica of the sol expressedas SiO the clay, and the aluminum compound expressed as A1 0 v being in:the range of 1:0.5 to

I 10.0:,0.1 to .0025,the proportion of binder to. fiber being discrete,amorphous silica particles having an, average diameter of from 12 1020millimicrons, a kaolin having an average particle size less than '10microns, and an alumi- C.,' and then heating. the dried fiber articlecomprising a particle size less than-10 microns, and a I 11. A'bonde'dinorganic fiber article comprising'a block I oi'glass fibers bonded withthe-dried and heated residue of a'binder comprising an aquasol' ofdense, substantially I 10:0:0.1 to .0025, said residuebeing present inthe proportion of. 15 to .35 by 7 weight [and drying having beenefiected at a temperature of up to 260? C. and heating having beenefiected at'a temperature of above 300C.

12. A bonded inorganicfiber article comprising a sheet of asbestosfibers bondedjwith the dried and heated residue of a binder comprisingan aquasol of dense, substantially discrete, amorphous silica particleshaving an ameter'ot from 12 to millimicrons, a kaolin having an averageparticle size less thanv 10' microns, and an alumi- I the weightproportions of the silica of the nnm formate, sol, expressed v as SiOmate expressed as A130 10.0 :01 to .0025, said residue being present inthe proportion of 15 to by the kaolin, and the aluminum for ing beeneliectedat a temperatureof above 300" C.

References Cited in the file of this patent UNITED STATES PATENTSaverage di- I being in the range of 1:05 to v 7 weight and drying havingbeen I effected at a temperature of up to 260C. 'and'heating hav

9. IN A PROCESS FOR BINDING INORGANIC FIBERS THE STEPS COMPRISINGFORMING A SHAPED MASS OF THE FIBERS, IMPREGNATING THE MASS WITH A BINDERCOMPRISING AN AQUASOL OF DENSE, SUBSTANTIALLY DISCRETE, AMORPHOUS SILICAPARTICLES HAVING AN AVERAGE DIAMETER OF FROM 12 TO 20 MILLIMICRONS, AKAOLIN HAVING AN AVERAGE PARTICLES SIZE LESS THAN 10 MICORON, AND ANALUMINUM FORMATE, THE WEIGHT PROPORTIONS OF THE SILICA OF THE SOLEXPRESSED AS SIO2, THE KAOLIN, AND THE ALUMINUM FORMATE EXPRESSED ASAL2O3 BEING IN THE RANGE OF 1:0.5 TO 10.0:0.1 TO .0025, AND THE BINDERHAVING A PH IN THE RANGE OF 2 TO 7.5 AND HAVING A SOLIDS CONTENT OF FROM5 TO 30% BY WEIGHT, THE PROPORTION OF BINDER IN THE INORGANIC FIBERSBEING FROM 5 TO 50% BY WEIGHT ON THE DRY SOLIDS BASIS, DRYING THEBINDER-IMPREGNATED FIBERS AT A TEMPERATURE UP TO 260* C., AND THENHEATING THE DRIED PRODUCT TO ABOVE 300* C.